Setup user dashboard

[mononoken]

To do: What is the main goal of the dashboard? It should give user's a quick look at what has changed since they last used, including notifications raised and potentially changes that have happened to shared journals.

• Show user's journals (potentially with a list of changes)
• Show user's notifications

Extra (original issue text):

Originally, I had the idea of when the user is signed in, they would view different things at the root address based on conditionals. These were:

• If user had no journals, redirect to new journal page
• If user had one journal, open the journal's notes index
• If user had multiple journals, open the journal index

However, upon exploring implementation of this, I decided this may be a poor idea. The idea was designed to make navigation simple for the user, but it may be confusing that the user uses the same address for multiple different pages.

Instead, I think it would be better simply for the user to see a dashboard if they are logged in, and ignore all these other conditions. The dashboard should give easy access to all of these previous ideas.

[mononoken]

Dashboard has been implemented. It does not follow the exact logic of this previous post.